1. Field of the Invention
This invention relates to methods and instrumentation for nondestructively measuring constituents, such as protein, moisture and oil in nonhomogeneous samples using near-infrared radiation, and particularly the rapid near-infrared measurement of such nonhomogeneous samples. More particularly, this invention provides an easy to use, low-cost instrument for analyzing constituents of nonhomogeneous samples, such as grain samples.
2. Description of the Prior Art
Near infrared measuring instruments that provide an accurate measure of constituents, such as protein, moisture and oil in nonhomogeneous organic products and other products utilizing near-infrared radiation are known in the art and have become commercially successful. Such instruments are particularly useful for measuring protein, oil and moisture in cereal grain in a totally nondestructive mode to a high degree of accuracy. Such instruments are commercially available from Trebor Industries, Inc. in Gaithersburg, Md. For example, in the grain industry, thousands of country elevators are currently using the TREBOR-90XL to provide protein and moisture measurements in wheat and barley. Similarly, in the food industry, the TREBOR-99 and the TREBOR-30A instruments are widely used in the near-infrared analysis of snack food, candy products, etc. These instruments are described in U.S. Pat. Nos. 3,286,327, 4,379,238, 4,404,462, 4,466,076 and 4,692,620, each assigned to Trebor Industries, Inc.
Although these known instruments have proven to be commercially successful, they, nevertheless, do have certain limitations. One such limitation is that these known devices require successive measurements from multiple locations, so that the resultant constituent measurements represent a meaningful average of the total product. Taking these multiple successive measurements of a single nonhomogeneous sample can result in larger time consumption and additional mechanical complexity. Specifically, the prior art devices require the nonhomogeneous sample to be moved, then stopped, in front of the near-infrared source and detector, and measurements made. The sample to be analyzed must then be again moved, stopped and measured wherein this process is repeated several times. In general, this process has to be done approximately 10 to 20 times in order to provide acceptable accuracy and precision. The process of repeatedly stopping, moving and measuring a single nonhomogeneous sample to obtain its constituent measurements can be burdensome and time consuming, typically lasting thirty seconds or longer. (See U.S. Pat. No. 4,692,620).
Further, accomplishing these multiple starts and stops requires the use of mechanical components which have an inherent lower reliability and add to the instrument's overall complexity.
While a number of prior art devices have proposed fiber optic containing assemblies for transmitting energy from a source to a sample, the use of fiber optics will lead to undue expense in the cost of manufacture. While fiber optics have many unique characteristics, we have found these characteristics to be unnecessary in the present application of near-infrared analytical technology.
Thus, there is a great need for an accurate, reliable near-infrared instrument having increased sample measuring speed and which is not subject to the mechanical "weakness" and complexity inherent in the current generation of instruments. Further, there is a need for an inexpensive analytical instrument which does not employ fiber optic technology in the interest of maintaining costs to manufacture at a minimum.